How would I set a precise width of a road comprised of multiple edges?
My suggestion is to use a curve which will keep the segments of consistent size.

1.) Create the curve:



Create a plane for the road surface (although you could use a cube) and loop cut it multiple times (the more the merrier) and scale it out:


Add the Curve modifier to the plane and select the curve.  You can also scale it to the desired length:


Finally, use the MeasureIt addon (included with Blender) and proportional editing to get the segment the exact width you want.